In an experiment, a scientist place a number of fleas in a glass jar. They quickly jumped out. He then replace the fleas back into the jar and placed a glass plate across the top opening. The fleas began jumping and hitting the glass plate, falling back down into the jar. After a while, the fleas, conditioned to the presence of the glass plate, began jumping slightly below the glass plate, so as not to hit it. The scientist then removed the glass plate as it was no longer need to keep the fleas in the jar. Do you create your own “glass plates” that keeps you restricted?